Interpretive Summary: Metarhizium anisopliae is being studied for use as a biological control for wireworms in British Columbia (BC), Canada and a Canadian isolate of the fungus has shown promise based on laboratory and greenhouse studies. Several years of field data have shown mixed results when the fungus was applied by a variety of application methods, however. The reported research sought to increase understand about some of the biotic and abiotic factors influencing fungus efficacy. Characteristics of three native and one commercial isolate of M. anisopliae were evaluated, including growth and spore production, mass production suitability using solid substrate fermentation, compatibility with agri-chemicals, response to soil type and moisture content, and pathogenicity toward several species of the European and North American wireworms. In field trials with the commercial isolate against wireworm in corn and potatoes.

Technical Abstract:
A Canadian isolate of Metarhizium anisopliae has shown promise as a biological control for wireworms based on repeated success in laboratory and greenhouse studies but field efficacy has been inconsistent. Laboratory experiments designed to explain these mixed results have pointed to certain biotic and abiotic factors as influential factors in efficacy. Specifically, we report the effect of moisture in different soil types on wireworm mycosis, the effect of different isolates on different species of wireworms, and the relative production characteristics of isolates of interest. Of the insecticides tested, hexahydroxyl significantly reduced M. anisopliae colony growth; clothianidin, halofenozide, imidacloprid, spinosad, and thiamethoxam had no effect. Conidia arising from colonies grown on agar containing thiamethoxam showed a 10% reduction in germination. Agar containing the fungicides captan and thiophanate methyl severely restricted M. anisopliae colony growth. Fungus infection and mortality is able to proceed with medium to very high soil moisture content, but is inhibited in dry soil, using sand, clay and organic soils. Isolates derived from cadavers of Agriotes obscurus, A. lineatus, and Limonius canus caused moderate levels of mycosis in A. lineatus and A. sputator, and high levels in A. obscurus. All isolates caused only lower levels of mycosis in L. canus. All three isolates, even though superior in virulence, were very inferior in spore production to the commercial strain F52.
The M. anisopliae strain F52 (also known as BIO1020, BIPESCO-5) was field-tested in 2006 in combination with the insecticides clothianidin and spinosad in potato and corn. Improved yield was observed in corn. Treating corn seeds with conidia increased the yield of corn, and if that effect is the result of causing wireworm mortality (in contrast to a repellent or nutrient effect), then an even greater effect can be expected by using the more virulent isolates.